Heat-treatment-free aluminum alloy material and preparation method thereof

Abstract

The invention belongs to the technical field of aluminum alloy treatment, and particularly relates to a heat treatment-free aluminum alloy material and a preparation method thereof, the heat treatment-free aluminum alloy material comprises 6-11% of Si, 0-0.5% of Fe, 0-0.8% of Cu, 0.3-0.6% of Mn, 0.1-0.4% of Mg, 0-0.25% of Zn, 0.05-0.2% of Ti, 0.01-0.03% of Sr, and the balance of A1; the method further comprises the steps that firstly, pure aluminum and recycled clean waste aluminum are heated to obtain molten aluminum, Si and Mn are added into the molten aluminum, heat preservation is conducted for 1 hour at the temperature of 780 DEG C, complete alloying is conducted, and liquid A is obtained; 2, adding pure aluminum or clean recycled aluminum into the liquid A, and then reducing the temperature to 700-730 DEG C to obtain liquid B; 3, Mg, an Al-Ti intermediate alloy and an Al-Sr intermediate alloy are added into the refined molten aluminum B through spectral analysis, and a liquid C is obtained. The heat treatment-free aluminum alloy has the beneficial effects that the performance of the heat treatment-free aluminum alloy can be remarkably improved without adding cobalt and zirconium metals, and the use cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy treatment, and particularly relates to a heat-treatment-free aluminum alloy material and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of integrated die-casting for new energy vehicles, large automotive structural parts such as integrated die-cast rear floors, battery housings, wheel covers, subframes, and shock towers have been vigorously developed in the direction of integration and high efficiency with the breakthrough of ultra-large tonnage die-casting machine technology.

[0003] Aluminum alloy die-cast parts have good mechanical properties. During the production of automotive die-cast parts, heat treatment will cause problems such as deformation and surface blistering of automotive die-cast parts, and the subsequent shaping difficulty and scrap rate will increase significantly. Currently, the most common method is to add high-value cobalt and zirconium metals during the heat-treatment-free aluminum alloy process. Using cobalt and zirconium metals can greatly improve the properties of heat-treatment-free aluminum alloy (tensile strength ≥ 240 MPa, yield strength ≥ 110 MPa, and elongation after fracture ≥ 6%), but the cost of using cobalt and zirconium metals is relatively high, and the recycling effect is poor. Summary of the Invention

[0004] The purpose of the present invention is to provide a heat-treatment-free aluminum alloy material and a preparation method thereof to solve the above problems.

[0005] The present invention achieves the above purpose through the following technical solutions:

[0006] A heat-treatment-free aluminum alloy material, comprising Si with a mass percentage content of 6 - 11%, Fe with a mass percentage content of 0 - 0.5%, Cu with a mass percentage content of 0 - 0.8%, Mn with a mass percentage content of 0.3 - 0.6%, Mg with a mass percentage content of 0.1 - 0.4%, Zn with a mass percentage content of 0 - 0.25%, Ti with a mass percentage content of 0.05 - 0.2%, and Sr with a mass percentage content of 0.01 - 0.03%, and the balance being Al.

[0007] Preferably, the heat-treatment-free aluminum alloy further comprises: Ni with a mass percentage content of 0 - 0.05%, Sn with a mass percentage content of 0 - 0.05%, B with a mass percentage content of 0 - 0.1%, V with a mass percentage content of 0 - 0.1%, and impurities with a mass percentage content of not more than 0.15%, wherein the mass percentage content of a single impurity is less than 0.05%.

[0008] Preferably, a preparation method of a heat-treatment-free aluminum alloy material comprises the following steps:

[0009] Step 1: Heat pure aluminum and clean recycled waste aluminum at 640 - 700 °C to obtain aluminum liquid. At a temperature of 730 - 780 °C, add Si and Mn to the aluminum liquid, and keep it at 780 °C for 1 hour until complete alloying to obtain Liquid A.

[0010] Step 2: Add pure aluminum or clean recycled aluminum to Liquid A, then lower the temperature to 700 - 730 °C to obtain Liquid B. At a temperature of 700 - 730 °C, refine the aluminum liquid by blowing a refining agent into it through nitrogen.

[0011] Step 3: Through spectral analysis, add Mg, Al-Ti master alloy, and Al-Sr master alloy to the refined Liquid B of aluminum to obtain Liquid C, that is, the heat-treatable aluminum alloy is obtained. At a temperature of 690 - 710 °C, introduce nitrogen into Liquid C for hydrogen removal.

[0012] Preferably, in Liquid C in Step 3, the mass percentage content of Si is 7 - 10%; the mass percentage content of Fe is 0.1 - 0.5%; the mass percentage content of Mn is 0.4 - 0.5%; the mass percentage content of Mg is 0.2 - 0.3%.

[0013] Preferably, after the hydrogen removal treatment of Liquid C in Step 3, the metallographic pinhole detection should reach Level 2 or above in the JB / T7946.3 - 2017 standard.

[0014] The beneficial effect is that in the technical solution of the present invention, the heat-free aluminum alloy has a mass percentage content of 6-11% Si, a mass percentage content of 0-0.5% Fe, a mass percentage content of 0-0.8% Cu, a mass percentage content of 0.3-0.6% Mn, a mass percentage content of 0.1-0.4% Mg, a mass percentage content of 0-0.25% Zn, a mass percentage content of 0.05-0.2% Ti, and a mass percentage content of 0.01-0.03% Sr, and the balance is Al. Si within this range can not only make the heat-free aluminum alloy have better tensile strength and yield strength, but also make the heat-free aluminum alloy have better casting performance and corrosion resistance. Fe is an alloying element, and its mass percentage content is set to 0-0.5%. The Fe element within this range often exists in the alloy in the form of a coarse needle-shaped Fe-rich phase. Although it can improve the mechanical properties of the alloy, it also seriously splits the Al matrix, causing a sharp drop in elongation. However, for castings produced by die casting, adding a certain amount of Fe can reduce the tendency of castings to stick to the mold; adding Mn to Al-Si alloy can reduce the harmful effects of the Fe-rich phase in the alloy, transforming the needle-shaped β-Al5FeSi phase into a Chinese character-shaped or block-shaped α-Al5(Fe,Mn)3Si2 phase, and improving the elongation and strength of the alloy. In addition, the atomic radius of Mn is quite different from that of Al, so the addition of Mn will increase the degree of lattice distortion of the alloy, and can significantly refine the grains, increase the alloy grain boundaries, and significantly improve the mechanical properties of the alloy. However, a better strengthening effect will only be achieved when the mass ratio of Mn / Fe is about 3, so a larger Mn content needs to be added. The Mg element can play the role of strengthening phase, forming a compound phase with Si in the heat-treatment-free aluminum alloy, thereby strengthening the heat treatment effect; the Ti element can provide crystal nuclei in the aluminum liquid, making the grains of the heat-treatment-free aluminum alloy finer and improving the mechanical properties; the Sr element can change the coarse flake metal phase of the Si element in the heat-free aluminum alloy into a point-like phase, and the flake aluminum phase into an α phase. The compound phase formed by the addition of Mn, Mg, Ti, and Sr elements can replace the metal phase formed by high-value Mo and Zr elements, and play the role of replacing traditional high-value cobalt and zirconium metals. In this way, the performance of the heat-treatment-free aluminum alloy can reach a tensile strength ≥240MPa, a yield strength ≥110MPa, and an elongation after fracture ≥6% without the addition of cobalt and zirconium metals, thereby reducing the cost of use and improving the recycling effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments are briefly introduced below. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further explained below:

[0017] An embodiment of the present invention provides a heat - treatable aluminum alloy, which contains Si with a mass percentage content of 6 - 11%, Fe with a mass percentage content of 0 - 0.5%, Cu with a mass percentage content of 0 - 0.8%, Mn with a mass percentage content of 0.3 - 0.6%, Mg with a mass percentage content of 0.1 - 0.4%, Zn with a mass percentage content of 0 - 0.25%, Ti with a mass percentage content of 0.05 - 0.2%, and Sr with a mass percentage content of 0.01 - 0.03%, and the balance is Al.

[0018] The mass percentage content of the Si can specifically be 7%, 8%, 9%, 10%, 11%.

[0019] The mass percentage content of the Fe can specifically be 0.001%, 0.005%, 0.01%, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%.

[0020] The mass percentage content of the Mn can specifically be 0.3%, 0.4%, 0.5%, 0.6%.

[0021] The mass percentage content of the Mg can specifically be 0.1%, 0.2%, 0.3%, 0.4%.

[0022] The heat - treatable aluminum alloy further includes impurities with a mass percentage content of not more than 0.15%, wherein the mass percentage content of a single impurity is less than 0.05%.

[0023] In the technical solution of the present invention, the as-cast aluminum alloy contains Si with a mass percentage content of 6-11%, Fe with a mass percentage content of 0-0.5%, Cu with a mass percentage content of 0-0.8%, Mn with a mass percentage content of 0.3-0.6%, Mg with a mass percentage content of 0.1-0.4%, Zn with a mass percentage content of 0-0.25%, Ti with a mass percentage content of 0.05-0.2%, Sr with a mass percentage content of 0.01-0.03%, and the balance is Al. Si within this range can not only endow the as-cast aluminum alloy with better tensile strength and yield strength, but also make the as-cast aluminum alloy have better casting performance and corrosion resistance. As an alloying element, the mass percentage content of Fe is set to 0-0.5%. Fe elements within this range often exist in the alloy in the form of large needle-shaped Fe-rich phases. Although it can improve the mechanical properties of the alloy, it also seriously cuts the Al matrix, resulting in a sharp drop in elongation. However, for castings produced by die-casting, adding a certain amount of Fe can reduce the tendency of the casting to stick to the mold; when Mn is added to the Al-Si alloy, it can reduce the harmful effects of Fe-rich phases in the alloy, change the needle-shaped β-Al5FeSi phase into the Chinese character-shaped or block-shaped α-Al5(Fe,Mn)3Si2 phase, and improve the elongation and strength of the alloy. In addition, the atomic radius of Mn is quite different from that of Al, so the addition of Mn will increase the degree of lattice distortion of the alloy, significantly refine the grains, increase the grain boundaries of the alloy, and significantly improve the mechanical properties of the alloy. However, a better strengthening effect can be achieved only when the mass ratio of Mn / Fe is about 3. Therefore, a relatively large amount of Mn needs to be added. The Mg element can play a role in strengthening the phase, forming a compound phase with Si in the as-cast aluminum alloy to enhance the heat treatment effect; the Ti element can provide crystal nuclei in the molten aluminum, making the grains of the as-cast aluminum alloy finer and improving the mechanical properties; the Sr element can change the large plate-like Si phase in the as-cast aluminum alloy into a dot-like shape, and the plate-like aluminum phase into the α phase. The compound phases formed by the addition of Mn, Mg, Ti, and Sr elements can replace the metal phases formed by high-value Mo and Zr elements, playing the role of replacing traditional high-value cobalt and zirconium metals.

[0024] The as-cast aluminum alloy further contains Cu with a mass percentage content of 0-0.8%. For example, the mass percentage content of Cu is 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%. The addition of Cu can improve the tensile strength, yield strength, and elongation of the as-cast aluminum alloy through solid solution strengthening.

[0025] The as-cast heat-treatable aluminum alloy further includes Zn with a mass percentage content of 0 to 0.25%. For example, the mass percentage content of Zn is 0.05%, 0.10%, or 0.2%. Adding Zn can improve the workability and fluidity of the as-cast heat-treatable aluminum alloy, etc.

[0026] The present invention also provides a method for preparing an as-cast heat-treatable aluminum alloy, comprising the following steps:

[0027] Heating pure aluminum and recycled clean scrap aluminum at 640 to 700 °C to obtain molten aluminum;

[0028] At a temperature of 730 to 780 °C, adding Si and Mn to the molten aluminum and holding at 780 °C for 1 hour until complete alloying to obtain Liquid A;

[0029] Adding pure aluminum or recycled clean aluminum to Liquid A and reducing the temperature to 700 - 730 °C to obtain Liquid B.

[0030] At a temperature of 700 to 730 °C, refining the molten aluminum by blowing a refining agent into the molten aluminum through nitrogen.

[0031] Through spectral analysis, adding Mg, Al-Ti master alloy, and Al-Sr master alloy to the refined Liquid B of aluminum to obtain Liquid C;

[0032] At a temperature of 690 to 710 °C, passing nitrogen into Liquid C to remove hydrogen.

[0033] The as-cast heat-treatable aluminum alloy is obtained from the Liquid C. Among them, the as-cast heat-treatable aluminum alloy contains Si with a mass percentage content of 6 to 11%, Fe with a mass percentage content of 0 to 0.5%, Cu with a mass percentage content of 0 to 0.8%, Mn with a mass percentage content of 0.3 to 0.6%, Mg with a mass percentage content of 0.1 to 0.4%, Zn with a mass percentage content of 0 to 0.25%, Ti with a mass percentage content of 0.05 to 0.2%, and Sr with a mass percentage content of 0.01 to 0.03%, and the balance is Al.

[0034] Further, at least one of the following conditions is satisfied:

[0035] The mass percentage content of Si is 7 to 10%;

[0036] The mass percentage content of Fe is 0.1 to 0.5%;

[0037] The mass percentage content of Mn is 0.4 to 0.5%;

[0038] The mass percentage content of Mg is 0.2 to 0.3%;

[0039] Further, at least one of the following conditions is satisfied:

[0040] The heat - treatable aluminum alloy further includes Cu with a mass percentage content of 0 - 0.8%;

[0041] The heat - treatable aluminum alloy further includes Sr with a mass percentage content of 0.01 - 0.03%;

[0042] The heat - treatable aluminum alloy further includes Zn with a mass percentage content of 0 - 0.25%;

[0043] The heat - treatable aluminum alloy further includes Ti with a mass percentage content of 0.05 - 0.2%;

[0044] The heat - treatable aluminum alloy further includes Ni with a mass percentage content of 0 - 0.05%;

[0045] The heat - treatable aluminum alloy further includes Sn with a mass percentage content of 0 - 0.05%;

[0046] The heat - treatable aluminum alloy further includes B with a mass percentage content of 0 - 0.1%;

[0047] The heat - treatable aluminum alloy further includes V with a mass percentage content of 0 - 0.1%;

[0048] Further, the refining treatment includes the following steps:

[0049] Adjust the temperature of the B liquid to 700 - 730 °C, and blow nitrogen and a refining agent into the second mixed liquid.

[0050] The purity of the nitrogen > 99.99%.

[0051] Further, after the hydrogen removal treatment of the C liquid, the metallographic pinhole detection should reach above level 2 in the JB / T7946.3 - 2017 standard.

[0052] The preparation method of the heat - treatable aluminum alloy further includes the following steps:

[0053] The components and contents of the refined liquid B are measured by direct-reading spectroscopy; and addition or dilution treatment is carried out according to the measured components and contents to make the components and contents of the refined liquid C meet the standards, where the components and contents of the refined liquid C are 6-11% Si by mass percentage, 0-0.5% Fe by mass percentage, 0-0.8% Cu by mass percentage, 0.3-0.6% Mn by mass percentage, 0.1-0.4% Mg by mass percentage, 0-0.25% Zn by mass percentage, 0.05-0.2% Ti by mass percentage, and 0.01-0.03% Sr by mass percentage, with the balance being Al.

[0054] Comparative Example 1

[0055] The aluminum alloy of Comparative Example 1 contains 7% Si by mass percentage, 0.15% Fe by mass percentage, 0.1% Cu by mass percentage, 0.4% Mn by mass percentage, 0.3% Mg by mass percentage, 0.1% Zn by mass percentage, 0.15% Ti by mass percentage, 0.02% Sr by mass percentage, and the balance being Al.

[0056] Example 1

[0057] The aluminum alloy of Example 1 contains 7.5% Si by mass percentage, 0.20% Fe by mass percentage, 0.2% Cu by mass percentage, 0.4% Mn by mass percentage, 0.35% Mg by mass percentage, 0.08% Zn by mass percentage, 0.16% Ti by mass percentage, 0.025% Sr by mass percentage, and the balance being Al.

[0058] Example 2

[0059] The aluminum alloy of Example 2 contains 6.8% Si by mass percentage, 0.25% Fe by mass percentage, 0.2% Cu by mass percentage, 0.42% Mn by mass percentage, 0.4% Mg by mass percentage, 0.15% Zn by mass percentage, 0.18% Ti by mass percentage, 0.025% Sr by mass percentage, and the balance being Al.

[0060] Example 3

[0061] The aluminum alloy of Example 3 contains Si with a mass percentage content of 9%, Fe with a mass percentage content of 0.15%, Cu with a mass percentage content of 0.4%, Mn with a mass percentage content of 0.45%, Mg with a mass percentage content of 0.25%, Zn with a mass percentage content of 0.2%, Ti with a mass percentage content of 0.08%, Sr with a mass percentage content of 0.02%, and the balance Al.

[0062] Table 1 shows the performance test results of the aluminum alloys of Comparative Example 1 and Examples 1 to 3.

[0063] Project Tensile strength MPa Yield strength MPa Elongation after fracture % Comparative example 255 115 7 Example two 260 120 7.5 Example three 270 130 8.2 Example four 265 124 7.8

[0064] The tensile strength, yield strength, and elongation after fracture of the aluminum alloys of the comparative example and Examples 1 to 3 all reach the performance of cobalt and zirconium metals, which can reach the performance of existing heat-treatable aluminum alloys (tensile strength ≥ 240 MPa, yield strength ≥ 110 MPa, and elongation after fracture ≥ 6%).

[0065] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A heat-treatment-free aluminum alloy material, comprising 6-11% Si by mass, 0-0.5% Fe by mass, 0-0.8% Cu by mass, 0.3-0.6% Mn by mass, 0.1-0.4% Mg by mass, 0-0.25% Zn by mass, 0.05-0.2% Ti by mass, and 0.01-0.03% Sr by mass, with the remainder being A1.

2. The heat-treatment-free aluminum alloy material according to claim 1, characterized in that: The heat treatment-free aluminum alloy also includes: Ni with a mass percentage content of 0-0.05%, Sn with a mass percentage content of 0-0.05%, B with a mass percentage content of 0-0.1%, V with a mass percentage content of 0-0.1%, and impurities with a mass percentage content of no more than 0.15%, wherein the mass percentage content of a single impurity is less than 0.05%.

3. A method for preparing the heat-treatment-free aluminum alloy material according to any one of claims 1 to 2, the steps of which are as follows: Step 1: heat pure aluminum and recycled clean scrap aluminum at 640-700°C to obtain aluminum liquid, add Si and Mn to the aluminum liquid at a temperature of 730-780°C, keep the temperature at 780°C for 1 hour to completely alloy, and obtain liquid A; Step 2: Add pure aluminum or clean recycled aluminum to liquid A, then lower the temperature to 700-730°C to obtain liquid B. At a temperature of 700-730°C, refine the liquid aluminum by blowing a refining agent into the liquid aluminum by nitrogen; Step 3: Through spectral analysis, Mg, Al-Ti master alloy, and Al-Sr master alloy are added to the refined B aluminum liquid to obtain C liquid, that is, the heat-treatment-free aluminum alloy. Nitrogen is introduced into the C liquid at a temperature of 690-710°C to remove hydrogen.

4. The heat-treatment-free aluminum alloy material and preparation method according to claim 3, characterized in that: In the step 3, the mass percentage content of Si in the C liquid is 7-10%; the mass percentage content of Fe is 0.1-0.5%; the mass percentage content of Mn is 0.4-0.5%; and the mass percentage content of Mg is 0.2-0.3%.

5. The heat-treatment-free aluminum alloy material and preparation method according to claim 4, characterized in that: After the C liquid in step 3 is dehydrogenated, the metallographic pinhole detection must reach level 2 or above in the JB / T7946.3-2017 standard.